A manual liquid dispensing device is widely used, because it can spray liquid through a nozzle hole or orifice by manually squeezing a trigger to thereby compress the liquid. Since the sprayer of this type has a stainless steel ball check valve disposed in the intake portion and a free cylindrical valve disposed in a nozzle portion to move with respect of the opening and closing operation of the check valve as disclosed, for example, U.S. Pat. No. 3,685,739, has a complicated structure to thereby require sophisticated assembly steps. As the piston slidably mounted into a cylinder bore of this sprayer consists of a piston body interlocked to a trigger, a rubber cap-shaped piston washer slidably contained within the cylinder bore, and a returning coil spring, it necessitates a complicated automatic assembly line due to numerous number of components.
Accordingly it is an object of the present invention to provide a liquid dispensing device which can eliminate all the disadvantages of the conventional trigger operated liquid sprayer and can readily be automatically assembled into a simple structure.
The present invention provides a liquid dispensing device which can prevent the negative pressure buildup in the container during its priming time by inserting a cylindrical adapter having stepwise cylinder bore diameters and a hole perforated at the side wall thereof into the cylinder bore.
The present invention provides a liquid dispensing device which can prevent liquid form flowing into the space formed between the cylinder bore and bellows interposed between the adapter and the piston within the cylinder bore with a gap formed to communicate with a liquid container by separating part of the adapter end from the cylinder bore wall when the piston is reciprocately mounted into the cylinder bore for smooth spraying operation.